1. Field of the Invention
The present invention relates to a contact structure to be used in catalytic reactions wherein the reaction and distillation of the reaction system are carried on concurrently in the same column.
2. Related Art
Recently a new method of carrying out catalytic reactions, wherein the components of the reaction system are separable by distillation has been developed, concurrently, using the catalyst structures as the distillation structures. Such systems are described variously in U.S. Pat. Nos. 4,215,011; 4.,232,530; 4,242,530; 4,250,052; 4,302,356; and 4,307,254 commonly assigned herewith. Briefly, a structure described there is a cloth belt with a plurality of pockets spaced along the belt, which is then wound in a helical about a spacing material such as stainless steel demister wire. These units are then disposed in the distillation column reactor.
In addition, U.S. patent application, Ser. No. 307,120 filed Sept. 30, 1981, discloses a variety of catalyst structures for this use.
Also, the previously noted patents suggest other configurations such as cages of wire cloth to contain catalyst beads, immersed in liquid on a conventional sieve tray. This arrangement is disclosed to have the disadvantage of the restriction of vapor flow by the close weave of the wire, which may be compensated by allowing the beads to move freely in the cage, thereby causing attrition.
U.S. Pat. Nos. 3,629,478 and 3,643,543 to Haunschild disclose a reaction carried out in distillation column wherein catalyst is contained in the downcomers or external of the column, such that the catalytic reaction takes place on the trays in the column. The problem which arises is that the catalyst in the downcomers causes them to be in a flooded condition.
U.S. Pat. No. 2,403,672 discloses a process for catalytic isomerization wherein the upper two thirds of a distillation column is packed with a catalytic material in the column to fractionate the product.
The present invention provides an alternative means to carry out a catalytic distillation wherein the catalyst is not the fractionation structure, but which does not have the disadvantages described above for alternative methods. The present invention further provides a means or system wherein the catalyst contact structure is present in the reactor distillation column and does not impede the flow of vapor or cause flooding.